1. Field of the Invention
The present invention relates to an organic EL element array used for a display, an exposure light source for an electrophotographic photosensitive member, and a lighting equipment.
2. Related Background Art
A self-emitting device corresponding to a flat panel is recently noticed. The self-emitting device includes a plasma display element, a field emission element, an electroluminescent (EL) device, and the like.
Of these devices, research and development have dynamically been progressed particularly for an organic EL element. An area color display of a single green color to which colors such as blue and red may be added has been manufactured and development to a full color display is being activated at present.
As a method of manufacturing a conventional organic EL panel adopting an independent three-color emission system for respectively emitting lights of different wavelengths independently of one another, Japanese Patent Application Laid-Open No. H05-258859 discloses a method of forming a transparent electrode pattern on a glass substrate using ITO and the like, then setting a shadow mask made of an insulating material on the substrate, and forming individual organic layers.
Further, Japanese Patent Application Laid-Open No. H11-214157 discloses a technique for separate color application of RGB in which adjacent pixels are formed such that a gap therebetween is filled with a light-emitting layer or electron-transporting layer or they overlap each other.
As shown in FIG. 1, these are techniques for evaporating an organic material in a vacuum chamber in which a mask is inserted between a substrate and an evaporation source to form an organic material layer at a desired location. FIG. 1 is a schematic view for explaining a conventional technique for evaporating an organic EL element through a mask. In the figure, reference numeral 1 denotes a substrate, reference numeral 2 denotes an evaporation mask, reference numeral 3 denotes an evaporated film, and reference numeral 4 denotes an organic material.
When carrying out separate color application of RGB by means of the mask evaporation, there has been a problem that an effective emission area (aperture ratio) becomes smaller as the definition becomes higher.
For example, when preparing a full color panel of 200 ppi, the pixel pitch thereof is approximately 127 μm and moreover, in order to display RGB in one pixel, each pixel region will have a width that is ⅓ (approximately 42 μm in the case of stripe) of the pixel pitch. In order to form organic EL elements of the respective colors in these pixel regions without causing color mixing, a width of a region capable of actually emitting light will become approximately 20 μm when assuming an alignment margin of ±10 μm.
Moreover, when the above-mentioned highly accurate, separate color application is to be attained by use of a mask, there has been a problem that because a region of a uniform film thickness will become small due to the thickness of the mask or the clearance between the mask and a substrate, an effective emission region becomes smaller.
In particular, with an organic EL element having a top emission structure for performing active matrix driving such as shown in FIG. 7, although a driving circuit can be formed under a pixel electrode and it is therefore theoretically possible to realize an aperture ratio of 90% or more, such a high performance cannot sufficiently be exploited due to the above-mentioned problems. Here, FIG. 7 is a sectional view of a conventional organic EL element having a top emission structure. In the figure, reference numeral 27 denotes a transparent electrode, 28 denotes an organic light-emitting layer, 29 denotes a reflective electrode, 30 denotes a source region, 31 denotes a drain region, 32 denotes a gate electrode, 33 denotes a drain electrode, and 34 denotes a glass substrate.